Sensor for measuring a length or an angle

ABSTRACT

An electric servo steering arrangement and method for motor vehicles with a rotational angle sensor configuration for acquisition of the position of the steering movement has a support plate rotating relative or corresponding to the steering movement, with at least one code track and at least one stationary sensor acting on the code track. The code track is disposed about the rotational axis of the support plate and has markings for generating a sequentially changing bit pattern and the 360° of the circumference divided by the number of markings on the circumference defines a clock angle (β). The bit pattern is determined by a phase-shifted disposition of markings with respect to the fixed division of the clock angle (β).

The invention relates to an electric servo-steering arrangement formotor vehicles with a rotational angle sensor configuration according tothe preamble of claim 1 as well as to a method according to claim 14 and15.

The invention addresses a steering arrangement for motor vehicles withpower-assisted drive, in which via a rotational angle sensor a desiredsteering movement is detected, via regulation devices atheoretical-actual deviation is determined, thereupon a requiredadjustment moment is calculated and the appropriate power is supplied tothe power-assisted drive.

Various steering arrangements of this type are known in prior art. Inparticular, in recent times there are increasingly found steeringarrangements with electric power-assisted drive (DE 10141199A1) or,circumventing the mechanical coupling between steering wheel and wheels,with direct electric drive of the steering adjustment of the wheels.

For measuring the angle in prior art, Hall sensors are frequentlyemployed. Therein onto the rotatable part magnetic elements arefastened, whose polarity changes in a fixed time pattern. A Hall probecorrespondingly picks up the Hall voltage caused by the alternation ofthe magnetic field and outputs counter pulses. By counting out thecounter pulses the difference angle can be determined. Only through themarking of a start point, for example marked by several pulses with samepolarity or by an additional sensor configuration, can the absoluterotational angle be determined. In alternative embodiments, such as forexample introduced in DE 101 04 855 A1, the sequence of the counterpulses is utilized as additional information. However, in this casethree sensors are required.

In comparison with the utilization of analog signals, the counting ofcounter pulses offers the advantage that the signal-to-noise ratio issignificantly increased, which means interferences have a lesser effecton the quality of the signal analysis.

Apart from the known advantages of such steering arrangements, such asfor example the low energy consumption or the capacity for goodadaptation to the desired steering behavior of the motor vehicle, thereis, however, a large number of new problems to be resolved.

In the first instance the response behavior and the precision of thewheel angle of the steering arrangement must be at least as good as in aconventional mechanical steering arrangement with hydraulic steeringbooster. Derived therefrom are several requirements made of the steeringarrangement. First, the driver's desire, which means the desired wheelangle must be determined by the steering arrangement. The angledetermination of the rotating components of the device with respect tothe non-rotating components must take place with certainty and rapidly.Subsequently, from the measured values rapidly and with certainty thenecessary power introduction into the electric power-assisted drive mustbe determined. Furthermore, the power assist or the electric drive,while circumventing the mechanical coupling, must be fed with minimumloss into the steering gearing. Lastly, the actually attained steeringangle must be measured in order to close the positioning regulationcircuit. Placed under the positioning regulation circuit, the regulationcircuit for the power control of the electronically commutated electricmotor must be closed.

However, the known systems have several distinct disadvantages. Thus,absolute values of the angles can only be acquired after passing througha relatively large angular range, for example, one complete rotation.Furthermore there is the risk of missing a marked starting point or acounter pulse, such that the angle measurement is erroneous. Moreover, astarting point must be defined. This leads either to a decrease of theresolution in the proximity of the starting point through the use of alonger pulse duration or to the need for a separate starting pointdetection sensor. In addition, most systems require several sensors, tosome extent even more than 2 sensors, for acquiring the angularposition.

The present invention addresses the problem of eliminating thedisadvantages of prior art. The problem addressed comprises, for one, tobring into agreement the commutation of the current flow with therotational position of the motor and, for another, to carry out theregulation very rapidly and smoothly so that no torsional fluctuationsare introduced into the steering system, which are perceived by thedriver as weaving or shimmy during the steering. This means that theangle of the rotor with respect to the stator of the electric motor mustbe acquired rapidly and with certainty. In addition the configurationmust be reliably, simply and economically realizable.

The subject matter of the invention deals with the acquisition bysensory means of the rotor angle as a basis for the optimal regulationof the steering system, in particular of the electronic control of theelectric motor.

The invention solves the problem of the sensory acquisition of theangles between the rotationally moved components with respect to thenon-rotationally moved components through an arrangement according toclaim 1 in simple manner and with comparatively low sensor expenditure.The dependent claims indicate further preferred embodiments. Claims 14and 15 contain the method for the solution of the problem.

According to the invention the electric servo-steering arrangement formotor vehicles comprises a rotational angle sensor configuration foracquiring the position of the steering movement, such configurationcomprising a support plate rotating relative or corresponding to thesteering movement, with at least one code track and at least onestationary sensor operating on the code track, wherein the code track isdisposed circularly about the rotational axis (Z) of the support plateand comprises markings for generating a successively changing bitpattern and the 360° of the circumference divided by the number of themarkings on the circumference defines a clock angle (β) and the bitpattern is determined by a phase-shifted configuration of markings withrespect to the fixed division of the clock angle (β). The selectedmarkings (41) are herein advantageously applied on the support plate (8)at some predefined sites at an offset (δ), such that the bit pattern atthese sites changes with delay with respect to the clock (β).

A preferred electric servo-steering arrangement according to theinvention includes a sensor configuration with two parallel orconcentric code tracks, such as will be described in further detail inthe following.

The readings recorder comprises a sensor unit, which is fixedly disposedwith the non-rotating component, comprised of two sensors and two codetracks, associated with the sensors and connected with the rotatablecomponent, on a support plate. On each of the two code tracks can befound an alternating ‘1’/‘0’ pattern at an equidistant angular spacingfor generating digital signals. The ‘1’/‘0’ patterns of the two codetracks are disposed exactly equally with respect to one another. Thismeans that if for a specific angular position the pattern of the onecode track just then changes from ‘1’ to ‘0’, the pattern of the othercode track changes exactly in the same direction. The pattern canpreferably be formed by permanent magnets or with a magnetization, forexample with a corresponding North-South polarity or through a dot maskor also by other comparable means, depending on the type of sensoremployed. The sensors can be, correspondingly in the case permanentmagnets are employed, Hall sensors or for dot masks simple opticaltransmitted light sensors comprised of light source andphotosemiconductor. In the case of the preferred utilization ofpermanent magnets for the representation of code tracks, a broad codetrack can simply be applied as a two-dimensional code track pattern,which at different spacings, viewed from the point of rotation, arescanned by two sensors.

The utilization of two different sensors with two associated code tracksserves primarily for two important purposes. For one, the one code trackthrough the uniform disposition of the markings provides a fixed clockinterval in relation to the angle of rotation. For another, the twosensors are disposed minimally offset with respect to one another.Thereby the change of the signal, caused by the change from marking ‘0’to ‘1’, is detected first in one of the two signals of the two codetracks. Therefrom the direction of rotation of the support plate cansubsequently be determined.

According to the invention on one of the two code tracks at somepredefined sites the alternating ‘1’/‘0’ pattern does not change inprecisely equidistant angular spacings, but rather slightly delayed oroffset. This means that this particular selected marking is applied atan offset onto the support plate. With these changes, which are delayedwith respect to the clock interval, a specific pattern can again beformed. The utilization of this pattern subsequently permits the rapiddetermination of the absolute angular position. After the first passageof a previously determined magnitude of the angular change, the initialdetection angle, which corresponds to the pattern length, the absolutevalue of the angle within a specified coding length with respect to thezero position and multiples of the coding length can subsequently bedetermined. The pattern length should always comprise the same anglelengths, i.e. the same number of clock intervals, but should comprisedifferent numbers of offsets of markings. The possible generatedpatterns and their assignment to fixed angle values are deposited in adata store in the form of a truth table or the patterns are such thatthey can be mathematically converted to the particular angle. For thispurpose the currently customary electronic stores and processors canadvantageously be utilized. It is here especially preferred if the bitpattern determined by the phase-shifted disposition of markings on thecode track change during the rotation of the support plate with eachclock (β) and this disposition is unique and unambiguous in order to beable to identify the position immediately and unambiguously. Thesespecified unambiguous patterns or words are deposited in the store andcan subsequently be compared with the actual pattern of the coding,based on which the position can be determined.

It can moreover be advantageous if the markings not disposed at anoffset are disposed at a partitioning of half a clock (β/2).

The advantage of the method according to the invention comprises thatafter the first passage through several changes of the marking up to thepassage of the defined angle change—the start detection angle—theprecise angle value can already be determined immediately with eachfurther change of the marking.

In a further development of the invention the clock signal of one of thetwo code tracks is omitted. This clock is subsequently determined afterthe passage through several changes of the marking of the remaining codetrack, for example through simple division of the number of changesdivided by the elapsed time. The offsets of the markings aresubsequently referred to the clock calculated thus and further processedin the same manner. Determination of the direction of rotation eithertakes place through a truth table, which contains the direction ofrotation, or through an offset of the markings, in which the start ofthe ‘1’ as well as also the end of the ‘1’ is delayed with respect tothe clock. Thereby, for example through simple difference formation ofthe sensor signal and the sensor signal constructed from the clock, apattern with positive and negative signal peaks can be generated. Thedirection of rotation is determined directly based on the simple test ofwhether the positive or the negative signal peaks are generated first.

In all embodiments of the method according to the invention the realsensor signal form(s) can additionally be sampled. Hereby the signalchange can be resolved further and even more precisely. Through thesampling of the signals further edge changes can be generated, based onthe counting of which intermediate values for the angle can bedetermined. The measuring resolution can thereby be increased further.

The aim of all measures shown in the invention is to determine the angleas rapidly and precisely and with as much certainty as possible. Forthis purpose, on the one hand, the physical limits with respect toproducible geometric values of corresponding markings and to thesignal-to-noise ratio and further factors must be observed. Depending onthe resolution, the acquisition of the angles in digital computersrequires words of different lengths. Through the correct size of theword length, for example 4 bits or 8 bits, the computing speed can besignificantly affected. It is necessary to differentiate between theword length for the computing operations as well as also for storageoperations. The optimum layout depends on the architecture of thehardware and through the introduced measuring methods can be harmonizedwith the required measuring resolutions and speeds. As parameters forthis purpose serve the length of the truth table, the sampling rate withrespect to the rotational speed, diameters and geometric dimensions ofthe markings and further variables.

The same method is applicable not only for the preferred angle ofrotation measurement but is also suitable for length measurements. Inthis case the rotation must be replaced by a translation and the anglereference by a length reference. The rotatable component is in this casea longitudinally displaceable component and the angle units and angleoffsets are correspondingly units of length and offsets of length. Forcode track configurations with the associated sensors magnetic means areespecially suitable and consequently preferred. However optical,capacitive or inductive means or their combinations can also beutilized.

A special application case for the utilization of the angle measurementcomprises the determination of the angle of the rotor with respect tothe pole shoes of the stator of an electric motor, for the applicationas electric power-assist in a steering system (servo-steering). This isespecially important for the correct and precise control ofelectronically commutated motors. Primarily during the start-up of themotor the correct direction of rotation must be ensured. The codinglength can here advantageously be set equal to the angle of one or morepole shoes.

The utilization of the bearing cover of the gearing arrangement, such asin particular when utilizing a ball screw, as the support plate of thecode tracks is especially advantageous.

On the preferred example of utilizing permanent-magnet markings on thecode tracks and the utilization of Hall sensors, the method for signalprocessing and analyzing will be shown in conjunction with schematicfigures. In the drawing depict:

FIG. 1 the schematic structure of a steering arrangement withpower-assisted booster,

FIG. 2 the disposition of the sensor configuration, its position withrespect to the pole shoes of the electric motor and the schematicassignment to the signal code bits,

FIG. 3 comprised of FIGS. 3 a and 3 b, the signal traces of the Hallsignals as well as the reference to the markings on the code tracks,

FIG. 4 comprised of FIGS. 4 a, 4 b and 4 c, the signal traces of theHall signals purged of the angle offset of the two sensors and thecombination signal,

FIG. 5 comprised of FIGS. 5 a, 5 b, 5 c and 5 d, the signal traces ofthe digitized Hall signals purged of the angle offset of the twosensors, as well as the reference to the markings on the code tracks andthe combination signal as well as the signal code bits,

FIG. 6 for another example the signal traces of the digitized Hallsignals purged of the angle offset of the two sensors and the digitizedcombination signal,

FIG. 7 a truth table for determining the instantaneous angle,

FIG. 8 comprised of FIGS. 8 a, 8 b, 8 c and 8 d, shows other examplesfor coding with the associated truth tables.

All of the illustrations in FIGS. 2, 3, 4, 5, 7 and 8 a refer to one andthe same example. FIG. 6 is only intended to demonstrate the option of asignal analysis of positive signal peaks 111 and negative signal peaks112. In FIGS. 8 b, 8 c and 8 d examples of other variants of the codingare shown in order to provide a reference of the way in which, after thespecification of the coding length C and of the start detection angleΔφ, a scheme for suitable angle offsets δ on the two code tracks 4, 5can be found and therewith a suitable definition of the markings 41, 51.

In the representation of the digitized signals the signal edge isclearly shown in the particular figures. The rise is determined by theparticular electronic circuitry utilized. However, the rise of thesignal edge is of subordinate significance for the analysis. Thereforein the illustrations the representation of the edges as being infinitelysteep has been omitted.

The schematic structure of a steering arrangement 29 with power-assistedbooster shown in FIG. 1 corresponds substantially to prior art. Itcomprises inter alia a steering wheel 20, a steering column 21, steeringgearing 22 and two tie rods 24. The tie rods 24 are driven by a toothedrod 23. For the power-assisted booster serves the drive unit formed ofthe components servo motor 25, sensor configuration 26 and ball screw27. The invention relates to the sensor configuration 26 and, in thespecific further development, in the disposition in a steeringarrangement for a motor vehicle. Therein the driver's desire is fedthrough the steering wheel 20 via (not shown) sensor circuitry as signal281 into a control device 28. From the sensor configuration 26 thesensor output signal 282, the instantaneous angle of rotation and,derived therefrom, the steering angle is fed into the control device 28.In the control device, the corresponding control voltage 283 for theelectric motor or servo motor 25 is determined therefrom and output tothe servo motor 25. For a sensitive and rapid regulation the rapidacquisition of the instantaneous angle φ is required. For the control ofthe servo motor 25 it is sufficient to know precisely the instantaneousposition of the stator (not shown here) with respect to the pole shoes 6of the stator (not shown here). The total angle φ over one complete oreven several rotations, from which the steering angle can be determined,does not need to be determined with high speed and can be determined bycounting the passages through the angular range of the coding length C.

FIG. 2 depicts for example the preferred disposition or the sensorconfiguration 26 comprised of the support plate 8, connected with therotatable component, with the two code tracks 4 and 5 with markings 41and 51, respectively, as well as the rotational axis Z and the sensorunit 3 connected with the non-rotating component and the sensors 1 and 2disposed thereon. The two sensors are advantageously disposed offset byan angle offset 32. The offset sensor configuration permits betterdetection of the running direction. Among the non-rotating componentsare to be counted for example the pole shoes 6 of the stator of theservo motor 25. The zero position of the angle of the system is markedby the zero position 31 on the sensor unit 3 and the zero position 81 ofthe support plate 8. For clarification of the markings, for example ofthe alternating North-South pole orientation of a permanent-magnetictrack, here the denotations ‘0’ and ‘1’ are chosen in the illustrationsor synonymously 0 (in white box) and 1 (in black box) or synonymously 0(in white box) and ▮.

Depicted here is the disposition of the code tracks in codirectionalpolarity. It is also possible to polarize the two code tracks in theopposite direction. To clarify the disposition of the code tracks in theopposite direction, in one of the two tracks only the ‘1’ needs to beexchanged against the ‘0’ label, and the ‘0’ against the ‘1’.

Each of the markings ‘0’ and ‘1’ have an angle of β/2. One pole pair 0/1therewith has an angle equal to clock β and corresponds to one bit inthe digital further processing of the signals. The coding length C isthe angular range for which the angle can be exactly determined afterthe first passage of the start detection angle Δφ. In the example theangle Δφcorresponds precisely to 4 bits or 4 clocks.

The second code track 5 has the task of specifying the clock β. Theclock signal β is generated from the Hall signal 10 of the sensor 2 whenthe support plate 8 is set into rotation.

As described above, on the first code track 4 an offset δ is introducedin some markings 41, which means one of the polarities, here for examplethe ‘1’ polarity, is extended by the angle δ.

In the example the servo motor 25 has 8 pole pairs and a coding lengthof 90°, which corresponds to a length of 16 bits at a start detectionangle Δφof 4 bits, which corresponds to an angle of 16.875°. From theoffsets δ are formed the signal code bits 7, which are drawn on fordetermining the angle φ. Greater word lengths permit better resolution,however at greater expenditure.

FIG. 3 a depicts the Hall signal 9 with the signal amplitude I of sensor1 with respect to the markings 41 of the first code track 4. In FIG. 3 bthe corresponding Hall signal 10 of sensor 2 is shown with respect tothe markings 51 of the second code track 5. Angle φ becomes greater withthe rotation in the rotation direction 12. The illustration encompassesa coding length C, which means 16 angles of a ‘0’/‘1’ marking 51. Amutual angle offset 32 of the two sensors 1 and 2 is shown by example.

Due to the angle offset 32 of the two sensors 1 and 2, the rotationdirection can be determined in simple manner. If the change from ‘0’ to‘1’ occurs in the Hall signal 9 before the Hall signal 10, the supportplate 8 rotates in rotation direction 12. Correspondingly, the supportplate rotates counter to rotation direction 12 if the change from ‘0’ to‘1’ occurs first in the Hall signal 10. The angle offset 32 must forthis purpose be less than β/2.

The angle offset 32 is not required for the further analysis, such thatit is corrected electronically or numerically. Therefore in all furtherfigures the Hall signals are corrected by the angle offset 32 of the twosensors 1 and 2, i.e. they are shown shifted to an angle offset of 0°.

FIGS. 4 a and 4 b show the Hall signals 9A and 10A, respectively, ofsensors 1 and 2, corrected by the angle offset, plotted over therotation angle. Furthermore is shown in FIG. 4 c the combination signal11 with the signal peaks 111. Here, as in FIG. 3, are shown the signalsfor the case that the polarities of the two code tracks are disposed inthe same direction. In the simplest case the combination signal can beformed as the difference from the Hall signals 9A and 10A.

In the next step digitizing of the Hall signals is carried out. Thefurther FIGS. 5 and 6 show a simple digitization to the two thresholdvalues of the signal, for example I signal >0 and I signal <0. Toincrease the resolution, however, sampling, for example to severalthreshold values of the Hall signals 9 and 10 can be carried out.

FIGS. 5 a and 5 b show the digitized Hall signal 9B and 10B of sensors 1and 2, respectively, plotted over the rotation angle φ and phase-shiftedabout the angle offset 32 of the two angle sensors. For clarificationthe markings 41, 51 of the code tracks 4 and 5 are shown. FIG. 5 cdepicts the digitized combination signal 11 with the signal peaks 111,which result from the angle offsets δ of markings 41 of code track 4.FIG. 5 d shows the signal code bits 7, generated from the signal peaks111, with the values 0 or 1, which are assigned to the particular clockβ. Based on the illustration the manner is evident in which, after thepassage of the first 4 clocks β, the sequence of signal code bits 7 “1 01 0” was generated from the combination signal 11. In our example thisvalue corresponds to precisely 16.875° measured from the start angle 81,31 or the start angle 81 plus the coding length C (in the example 90°).

The truth table shown in FIG. 7 which is associated with theillustrations in FIGS. 2, 3, 4 and 5, shows the manner in which theangle φ is determined in conjunction with the signal peaks 111 of thecombination signal 11 and the associated signal code bits.

In Table 1, the sequence of the angle detection and the structure of thetruth table is shown in conjunction with the example depicted in thefigures. If the support plate 8 starts to rotate in rotation direction12 from the zero position 81, 31, the clock β is passed through, i.e. anumber of ‘0’/‘1’ changes. Clock β corresponds to the angle φ which ishere shown in the sequence 5.625°, 11.250°. Through the angle offset δof the markings the signal peaks 111 in combination signal 11 andconsequently the signal code bits 7 are generated. This corresponds tothe signal code bits 7 shown in FIG. 5 d with the digital values 0 or 1.The store, which in our example has a word length of 4 bits, is filledbit by bit, as shown in the lower portion of Table 1. After passing theangle 16.875°, the store is filled with a complete 4-bit word of thesignal code bits 7. From now on, the instantaneous angle value can beread directly from the truth table, as shown in FIG. 7. TABLE 1 Table 1.It should be noted that, depending on the rotation direction, thestorage into the store must take place either at the highest or thelowest bit of the word in the store while shifting the bits alreadystored in the store. C Start of sequence Angle (φ)in° 5.625 11.25 16.87522.5 28.125 33.75 39.375 45 50.625 56.25 Clock (β) 1 2 3 4 5 6 7 8 9 10Signal (7) 1 0 1 0 0 1 1 0 1 1 code bit C Start of sequence Sequencestarts again Angle (φ)in° 61.875 67.5 73.125 78.75 84.375 90 5.625 11.2516.875 22.5 Clock (β) 11 12 13 14 15 16 1 2 3 4 Signal (7) 1 1 0 0 0 0 10 1 0 code bit Detected values (111), i.e. signal code bits (7) afterthe first passage through the sequence in rotation direction (12)according to FIG. 1 Angle (φ)in° Detected signal code bits (7) with4-bit word length 1 × β = 5.625 1 2 × β = 11.250 1 0 3 × β = 16.875 1 01 4 × β = 22.500 1 0 1 0 5 × β = 28.125 0 1 0 0 6 × β = 33.750 1 0 0 1 7× β = 39.375 0 0 1 1 8 × β = 45.000 0 1 1 0 9 × β = 50.625 1 1 0 1 10 ×β = 56.250 1 0 1 1 11 × β = 61.875 0 1 1 1 12 × β = 67.500 1 1 1 1 13 ×β = 73.125 1 1 1 0 14 × β = 78.750 1 1 0 0 15 × β = 84.375 1 0 0 0 16 ×β = 90.000 0 0 0 0 C + 1 × β = 95.625 0 0 0 1 C + 2 × β = 11.250 0 0 1 0C + 3 × β = 16.875 0 1 0 1 C + 4 × β = 22.500 1 0 1 0

TABLE 2 In Table 2 the store content is shown during the structuring ofthe zero position 81, 31 with the word length of 4 bits for theparticular clock β/angle φ. As is evident in conjunction with thestructuring of Table 1 and Table 2, the word length corresponds also tothe number of clocks until the first angle can be unambiguouslydetected, and therewith to the start detection angle Δφ/β. Structure ofthe truth table, passage at initial rotation Detected signal code bits(7) φ [°] with 4-bit word length C 5.625 — — — 1 11.250 — — 1 0 16.875 —1 0 1 22.500 1 0 1 0 28.125 0 1 0 0 33.750 1 0 0 1 39.375 0 0 1 1 45.0000 1 1 0 50.625 1 1 0 1 56.250 1 0 1 1 61.875 0 1 1 1 67.500 1 1 1 173.125 1 1 1 0 78.750 1 1 0 0 84.375 1 0 0 0 90.000 0 0 0 0 5.625 0 0 01 11.250 0 0 1 0 16.875 0 1 0 1 22.500 1 0 1 0

FIG. 8 shows also several patterns of truth tables as examples of themanner in which for different coding lengths C and start detectionangles Δφ with the associated word lengths Δφ/β a sequence of signalcode bits 7 can be defined, so that, after the initial passage of startdetection angle Δφ, with each further passage of angle β the absolutevalue of the rotational angle can be determined.

Our example is once again shown in FIG. 8 a. In FIGS. 8 b, 8 c, and 8 dillustrations of the coding lengths of 5, 8 and 10 and word lengths of 3bits, 3 bits and 4 bits, respectively, are given.

Based on the examples with the Tables, it is evident that the successivebit patterns, offset by angle β, are selected such that these are alwaysunambiguous and appear as unique patterns, thus are non-recurrent,wherewith a unique angle position detection is possible at any time bycomparing the measured patterns with the stored patterns.

FIG. 6 depicts for another example the digitized Hall signal 9B ofsensor 1 and the digitized Hall signal 10B of sensor 2 over the angle ofrotation and shifted in phase by the angle offset 32 of the two anglesensors. However, the markings are here so offset by angle δ that acombination signal 11 with positive signal peaks 111 and negative signalpeaks 112 is generated. From the time sequence of the occurrence of thepositive signal peak 111 and the negative signal peak 112 the directionof rotation is determined. If the positive signal peak 111 occurs beforethe negative signal peak 112, the support plate 8 rotates in rotationdirection 12. If the negative signal peak 112 occurs before the positivesignal peak 111, the support plate 8 rotates counter to the rotationdirection 12.

In the event it cannot be decided which signal peak 111 or 112 occursearlier, the signal edge of signal 9B is also utilized. If the signal 9Brotates from the low to the high value and if simultaneously thepositive signal peak 111 is detected, the support plate rotates inrotation direction 12. However, if the negative signal peak 112 isdetermined simultaneously, the support plate rotates counter to therotation direction 12.

In the especially cost-effective further development of the system thesensor 2 is omitted and the clocking signal 10B resulting therefrom isdetermined numerically from the elapsed time and the ‘0’/‘1’ changes ofthe signal 9B, as already described above. In this way, the clockingsignal 10B can be mathematically generated and all procedures describedabove for determining the angle can be applied.

However, the application of this cost-effective further developmentbrings about the degradation of the resolution, since at least three andrather more ‘0’/‘1’ changes are required for determining the digitized(clock) signal 10B.

Very good results can be obtained at a mean reading radius ofapproximately 42 mm and a magnetic pole distance of 1.5 to 3.5 mm. Thus64 pole changes of the magnetic field can be represented. This means 64complete periods of the Hall signal. At a sampling rate of 1/32 thisyields 4096 edge changes for each digitized signal 9B or 10B. Since twocoding tracks are available, overall 8192 edge changes result. Thisyields an angular resolution of the system of approximately 0.044°.

To improve the resolution, via a gearing with a gear transmission ratio,to the rotatable component can be coupled a component rotating at ahigher rotational speed, with which in this case the carrier plate 8 isconnected. In this manner with the same number of permanent magnets andHall sensors the angular resolution can be increased by the transmissionfactor of the gearing.

It is evident that all of the above described embodiments can also betransferred to optical, electrical, inductive or capacitive transducers.Moreover, lengths can also be measured in the same manner.

A special application case comprises the application of the abovedescribed arrangement for the regulated control of an electric motor orservo motor 25 for the driving of a steering system for motor vehicleswith electric power assist. In this case the problem consists ofensuring the commutation of the current flow depending on the angularposition of the rotor with respect to the stator of the servo motor 25.The current flow must be switched over so smoothly that no irregularmoment of torsion is output by the electric motor. For this purpose thesupport plate 8 is coupled with the rotor and the sensor unit with thestator of the electric motor. With the aid of the measurement result theposition of the rotor with respect to the pole shoes of the stator issubsequently determined. The coding length C and the clock β must bedefined according to the angle between the pole shoes 6.

1. Electric servo steering arrangement (29) for motor vehicles with arotational angle sensor configuration (26) for the acquisition of theposition of the steering movement comprising a support plate (8),rotating relative or corresponding to the steering movement, with atleast one code track (4) and at least one stationary sensor (1) actingon the code track (4), wherein the code track (4) is disposed circularlyabout the rotational axis (Z) of the support plate (8) and comprisesmarkings (41) for generating a sequentially changing bit pattern and the360° of the circumference divided by the number of markings (41) on thecircumference defines a clock angle (β), characterized in that the bitpattern is determined by a phase-shifted disposition of markings (41)with respect to the fixed division of the clock angle (β). 2.Arrangement as claimed in claim 1, characterized in that selectedmarkings (41) are applied on the support plate (8) at some predefinedsites with an offset (δ), such that the bit pattern at these siteschanges with delay with respect to the clock (β).
 3. Arrangement asclaimed in claim 1, characterized in that the markings (41) not disposedat an offset (δ) are disposed at a partitioning of half a clock (β/2).4. Arrangement as claimed in claim 1, characterized in thatconcentrically with the first code track (4) is provided a secondclocking reference code track (5) and at least one stationary sensor (2)operating on the code track (5), this code track (5) being developedwith the same number of markings (51) as the first code track (4), andthese markings being disposed equidistantly over the circumference andeach marking determining the clock angle (β).
 5. Arrangement as claimedin claim 4, characterized in that the two sensors (1, 2) operating onthe code tracks (4, 5) are disposed such that they are offset by a fixedangle (32) which preferably is maximally one half of the clock angle(β).
 6. Arrangement as claimed in claim 1, characterized in that the bitpattern determined by the phase-shifted disposition of markings (41) onthe code track (4) during the rotation of the support plate (8) within afixedly specified angular range (C) which encompasses the full 360° oronly a portion thereof, changes after each passage of a further clock(β).
 7. Arrangement as claimed in claim 6, characterized in that thesignal code bits (7), generated by the bit pattern, with a fixedlyspecified word length of, for example, 3, 4 or more bits, yield a dataword which can be unambiguously assigned to a fixed number of clocks (β)within the fixedly specified angular range (C), and consequently to adefined angle (φ).
 8. Arrangement as claimed in claim 1, characterizedin that the bit pattern (7) determined by the phase-shifted dispositionof markings on the code track (5) is changed after each clock position(β) and that this is unambiguous and unique and singular, wherewith theposition is unambiguously identifiably defined.
 9. Arrangement asclaimed in claim 1, characterized in that the code track (4, 5) and thesensor (1, 2) comprise magnetic, optical, capacitive or inductive meansfor defining and detecting the markings (41, 51), with magnetic meansbeing preferred.
 10. Arrangement as claimed in claim 1, characterized inthat the arrangement comprises electronic means (28, 281, 282, 283) forcontrolling and analyzing the angle of rotation sensor configuration(26), such as preferably a microprocessor control.
 11. Arrangement asclaimed in claim 10, characterized in that the singular patterns of thesignal code bits (7) are deposited in an electronic store as a referencewith the associated angular position of the support plate (8). 12.Arrangement as claimed in claim 11, characterized in that electronicmeans are provided for the control and regulation as a function of theposition of the angle of rotation of an electrically commutated motor(25) of the servo steering (29).
 13. Arrangement as claimed in claim 12,characterized in that the steering arrangement (29) includes a gearing(27) which comprises a ball screw (27) and the latter is operationallyconnected with the electrically commutated motor (25).
 14. Method fordetermining an angle in an electric servo steering arrangement (29) formotor vehicles by means of a rotational angle sensor configuration (26)for acquiring the position of the steering movement, wherein suchincludes a support plate (8), rotating relative or corresponding to thesteering movement, with at least one code track (4) and at least onestationary sensor (1) operating on the code track (4), wherein the codetrack (4) is disposed circularly about the rotational axis (Z) of thesupport plate (8) and comprises markings (41) for the generation of asuccessively changing bit pattern and the 360° of the circumferencedivided by the number of markings (41) on the circumference defines aclock angle β, characterized in that the bit pattern, determined by aphase-shifted disposition of markings (41) with respect to the fixeddivision of the clock angle (β), is read out with a sensor (1) byacquiring the position, after rotation of the support plate about one orseveral clock angles (β) in either direction of rotation a signal codebit (7) is determined for each clock by comparison with the fixed clockangle (β), the sequence of signal code bits (7) is stored in a firststore with a fixedly specified but freely selectable word length of twoor more bit word length, the stored signal code bits (7) are comparedwith a table, deposited in a second store, in which an assignmentbetween angles of rotation and words comprised of two or more bits,corresponding to the word length in the first store, are stored, andtherefrom the angle of rotation is determined.
 15. Method fordetermining an angle in an electric servo steering arrangement (29) formotor vehicles by means of a rotational angle sensor configuration (26)for acquiring the position of the steering movement, such configurationcomprising a support plate (8), rotating relative or corresponding tothe steering movement, with at least one code track (4) and at least onestationary sensor (1) operating on the code track (4), wherein the codetrack (4) is disposed circularly about the rotational axis (Z) of thesupport plate (8) and comprises markings (41) for the generation of asuccessively changing bit pattern and the 360° of the circumferencedivided by the number of markings (41) on the circumference defines aclock angle β, characterized in that the bit pattern, determined by aphase-shifted disposition of markings (41) with respect to the fixeddivision of the clock angle (β), is read out with a sensor (1) byacquiring the position, after rotation of the support plate about one orseveral clock angles (β) in either direction of rotation a signal codebit (7) is determined for each clock by comparison with the fixed clockangle (β), the sequence of signal code bits (7) is stored in a firststore with a fixedly specified but freely selectable word length of twoor more bit word length, the stored signal code bits (7) are analyzed inconjunction with a fixedly specified rule, with which an assignmentbetween angle of rotation and position is determined, and therefrom theangle of rotation is determined.